In the telecommunications industry, mobile telephone usage has increased dramatically through the construction and operation of mobile networks by mobile network operators (MNOs). Recently, mobile virtual network operators (MVNOs) have emerged as providers of cell phone services. The MVNOs typically do not own or operate the core communications network infrastructure, but instead contract with an MNO for the communications support while focusing on marketing to subscribers. MVNOs often have pre-established relationships with a certain customer base and are thus able to attract a new subscriber base for mobile communications services at a relatively low cost and risk, thereby providing an attractive partnership opportunity for MNOs to enhance resource utilization without high marketing costs normally associated with developing new subscribers. At the same time, such cooperative arrangements with MNOs provide the MVNO with a chance to enter the mobile market without significant initial investment and also to enhance their own branded services. In this manner, MVNOs and their agreements with MNOs are expected to create significant subscriber growth for the mobile communications industry as a whole. Discounted or free mobile to mobile calling is a feature offered by many MNOs for their subscribers, which provides an important incentive for attracting mobile subscribers. Thusfar, however, MVNO subscribers cannot obtain this service, as the MNO infrastructure does not allow for such selective discounting. Thus, there remains a need for improved communications systems and call rating techniques by which MVNO subscribers can be offered free or discounted mobile to mobile calling.